Method of making an insert and cast piston combination



April 30, 1968 J. 5. ms ET AL 3,380,139

METHOD OF MAKING AN INSERT AND CAST PISTON COMBINATION 1 Filed April 6. 1966 INVENTORS JOHN S. KIS ROBERT M. THE/SEN United States Patent 3,380,139 METHOD OF MAKING AN INSERT AND CAST PISTON COMBINATION John S. Kis, Racine, and Robert M. Theisen, Marinette,

Wis., assignors to Alum-Alloy Casting Co., Racine,

Wis., a corporation of Wisconsin Filed Apr. 6, 1966, Ser. No. 540,770 Claims. (Cl. 29-1565) This invention relates to a method of making an insert and cast piston combination. It is therefore related to the casting of an engine piston having an insert ring cast into the piston body.

It is well known to cast an insert ring into a piston manufactured by a casting process. Thus the insert ring is supported in a casting mold, and the molten met-a1 is poured into the mold to surround the ring and thereby locate and retain the ring in the piston body. Subsequently, the piston and/or the insert ring itself can be machined to the finish desired on the exterior. The insert ring is then available for reception of the usual expandable and contractable piston ring itself.

It is a general object of this invention to provide an improved method of making a combined piston body and insert ring in a casting process.

A more specific object of this invention is to provide a method of making an insert ring and a cast piston combination which can be readily and easily machined in a turning type of machining process so that the final product of the combination is the provision of a sturdy, easily manufactured, reliable, and relatively inexpensive piston.

Still another object of this invention is to provide a method of making a cast piston and insert ring therefor, wherein the insert ring is metallurgically bonded Within the piston body and thereto in a manner to minimize voids, cracks, separation lines, and the like, so that the finished product is an improvement over the cast pistons heretofore known. In accomplishing this object, it will be understood that casting an insert ring into a piston body may be done by either a chemical bonding or a mechanical bonding. In a chemical bonding, an iron insert ring may be cast into an aluminum piston body by inserting the iron ring into an aluminum bath, and then supporting the ring in the casting mold and pouring the molten aluminum metal around the ring. In the mechanical bonding, the ring may be pro-heated, and then placed into the casting mold and then have the molten aluminum poured around the ring. These examples of course presuppose that the insert ring is made of one metal and the piston body is made of another metal, as mentioned.

Still another object of this invention is to provide a method of making an insert ring and a cast piston combination, wherein the insert ring and the piston body are of different metals but the process is such that the completed piston, with the insert ring therein, can be turned for finishing the outer surface, as desired, but without commingling the cuttings of the piston body and the insert ring, at least through the initial or inspection-cut turning. This therefore permits the manufacturer to recover the cuttings removed from the piston body and have them all of one metal, say aluminum, assuming that to be the metal used in the casting of the piston body, and not have the recovered cuttings contaminated by the cuttings from the insert ring. In this object, it should be appreciated that the recovery of cuttings in the manufacture of pistons is an important consideration. If, for instance, the aluminum cuttings and the iron cuttings were to be commingled, then a separator would have to be employed, such as a magnetic separator, to separate out the iron cuttings so that only the aluminum cuttings Patented Apr. 30, 1968 ice could be recovered without contamination from the iron cuttings.

Still a further object of this invention is to provide a method of making an insert ring and piston combination wherein the ring is securely retained within the piston body so that it can be cut by a turning process after it is cast into the body and therewith. Further, it is significant to note that the process is arranged to result in an insert ring which is of suitable stock and location for the forming of a finish-cut groove therein for reception of the piston ring the user desires to insert into the groove.

Other objects and advantages become apparent upon reading the following description of the method which is described in conjunction with the drawings, wherein:

FIG. 1 is a longitudinal sectional view through the piston combination and the mold therefor, with the interior part of the mold removed.

FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1, with the line being slightly irregular as indicated.

FIG. 3 is an enlarged view of a fragment of FIG. 1;

FIG. 4 is a view similar to FIG. 3 but with a part of the piston cut away.

The drawings show the physical aspects of the invention, and the mold side parts 10 and 11 and the end or upper part 12 are all of a conventional nature and are separable and brought together in the common manner of using a mold for cast metal. Thus the parts 10 and 11 separate along the center plane designated by the dotted line 13 in FIG. 1 so that these parts 10 and 11 may move toward and away from each other in the usual manner. Actually, the design or invention can be employed in any of the standard molding or casting methods, including sand molds, permanent molds, plaster molds, and pressure die casting.

The drawings further show a piston body designated 14, and it will of course be understood that this is formed from a molten metal poured into the mold. Thus a central portion of the mold is not shown and has been removed and would be employed for forming the interior wall designated 16 of the piston body 14. Of course when the molten metal has hardened, then the parts 10, 11, and 12 can be opened or removed so that the remaining piston body 14 is provided as shown, or in any suitable form having an outer circumference, as designated by the line 17.

The mold parts 10 and .11 are shown provided with a doublestepped annular projection or tongue 18. The tongue 18 supports an insert ring 19 which has an annular groove 21. The tongue 18 and groove 21 are fitted so that the ring 19 can be fully supported by only one of the mold parts 10 and 11. Thus when the ring 19 is positioned in the one mold part 10 or 11, then the other mold part 10 or 11 can be closed upon the ring, and the mold may then be ready for pouring the piston body 14. It will be noted that the outer circumference 22 of the insert ring 19 is less than the piston body outer circumference 17. That is, the insert ring 19 is recessed or countersunk with respect to the piston body 14, see FIG 3 where the mold is removed. Thus the insert ring 19 is pre-grooved at 21 to mate with the mold halves 10 and 1-1 for support of the ring 19 in the mold during the pouring process. The molten metal forming the piston body 14 then is bonded to the ring 19 at the ring top 23, inside circumference 24 and bottom 26. All but the outer side of the insert ring 19, that is the side with the circumference 22, are bonded and completely contacted by the piston body 14 and its molten metal.

Particularly FIG. 2 shows the ring 19 formed on its inner surface 24 by serrations designated 27. These provide an interlock between the piston body 14 and the insert ring 19 itself. Thus the ring 19 can be machined by a turning process when it is desired to put a finish on the outer circumference of the insert ring 19. Of course the serrations 27 may be of other forms, but are generally teeth, as shown.

FIG. 3 shows the piston before it is finish-cut, and FIG. 4 shows it after it is finish-cut. Thus, it is common to make an inspection-cut on a cast piston, and this inspection-cut may be made anywhere say up to the outer circumference 22 of the insert ring 19. That is, it may be made along the circumference designated by the dot-dash line 28. Since this cut does not extend to the insert ring 19, all cuttings come only from the piston body 14. These cuttings may therefore be collected and reclaimed by a smelter, and of course they will not be contami nated with the cuttings from the ring 19 which is ordinarily of a different metal. That is, the body 14 may be an aluminum, and the ring 19 may be of an iron metal. It is important and desired that the two metals remain separated and this may be accomplished by this process in addition to the accomplishment of the improved bonding of the two metals along the surfaces 23, 24, and 26.

Next, the piston may be cut by a turning process, such as a grinding or a lathe process, or of course a combination thereof, so that a finish can be placed on the outer circumference of the combination. This cut may be along the circumference designated by theline 29, and this line may extend to the base of the ring-groove 21, as indicated. Finally, the ring 19 itself may be formed with a groove 31 cut therein by a turning process, such as a grinding process or any other suitable cutting process. Then of course the groove 31 is available for reception of the conventional piston ring, which is not shown.

FIG. 4 thus shows that the line 29 designates the final outer circumference, including a portion of the ring 19 exclusive of its groove 31. Thus it will be understood that it is important to have the entire method and arrangement such that the piston can be subjected to turn-cutting by which is mean turning on a lathe or grinding wheel so that the outer circumference of the piston body 14 and the insert ring 19 would be uniformly cut, in the conventional manner.

The countersinking of the ring 19, as shown in FIG. 3 with respect to the piston body 14, thus prevents the con tamination of the metals in the inspection-cutting process, and in fact in the further cutting process until the ring 19 is reached. Further, it provides for better bonding of the ring 19 with the body 14 since the latter overlaps the ring 19 as shown. Casting voids normal in previously known methods along the surfaces 23 and 26, are at least reduced in this method.

Also, having a full insert ring 19 for the cutting of its groove 31, provides adequate stock in the insert ring for the location, shape, and size of the groove 31, as desired.

While a specific method of this invention has been shown and described, it should be obvious that certain changes could be made in the embodiment and the invention should therefore be determined only by the scope of the appended claims.

What is claimed is:

1. LA method of making an insert and cast piston combination comprising the steps of positioning an insert ring in a casting mold of a diameter larger than that of said ring, said ring being spaced from the bottom of said mold and transverse to the retaining wall of said mold, pouring molten metal into said mold to form a piston with said ring being visable after removal of the piston from the mold, said metal contacting said insert ring on all sides of said insert ring except the outer side on the outer diameter of said insert ring, and said molten metal extending radially beyond the cylinder defined by said outer side with the radial extent being suflicient to provide that when said metal is hard it can be inspection-cut on a turning machine without cutting said insert ring while cutting uniformly along the entire length of said piston, solidifying said molten metal, inspection-cutting said piston on a turning machine along the length of said piston and to a radial depth short of said insert ring, finish turncutting said piston and said insert ring along the entire length of said piston and to a radial depth suflicient to finish-cut said outer side of said insert ring, and cutting a groove in said insert ring for reception of a piston ring.

2. The method of claim 1, including the step of forming said insert ring with teeth on the radial inner side and interlocking said teeth with said molten metal for securing said insert ring in said piston for turn-cutting said insert ring.

3. The method of claim 1, including the step of forming a tongue-and-groove interlock between said mold and said outer side of said insert ring for positioning of said ring in said mold while pouring said molten metal.

4. The method of claim 3, wherein said tongue-andgroove interlock is formed by forming a pre-groove on said outer side of said insert ring and by forming an annular projection on the portion of said mold mating with said pro-groove.

5. The method of claim 2, including the step of forming a pre-groove on said outer side of said insert ring, and forming an annular projection on the portion of said mold mating with said pre-groove, for positioning of said ring in said mold while pouring said molten metal.

References Cited UNITED STATES PATENTS 2,620,530 12/1952 Sulprizio 29'l56.5 2,685,729 8/1954 Daub 29--156.5 3,183,796 5/1965 Christen et a1. 92229 3,264,717 8/1966 Class et a1. 29156.5

JOHN F. CAMPBELL, Primary Examiner.

PAUL M. COHEN, Examiner. 

1. A METHOD OF MAKING AN INSERT AND CAST PISTON COMBINATION COMPRISING THE STEPS OF POSITIONING AN INSERT RING IN A CASTING MOLD OF A DIAMETER LARGER THAN THAT OF SAID RING, SAID RING BEING SPACED FROM THE BOTTOM OF SAID MOLD AND TRANSVERSE TO THE RETAINING WALL OF SAID MOLD, POURING MOLTEN METAL INTO SAID MOLD TO FORM A PISTON WITH SAID RING BEING VISABLE AFTER REMOVAL OF THE PISTON FROM THE MOLD, SAID METAL CONTACTING SAID INSERT RING ON ALL SIDES OF SAID INSERT RING EXCEPT THE OUTER SIDE ON THE OUTER DIAMETER OF SAID INSERT RING, AND SAID MOLTEN METAL EXTENDING RADIALLY BEYOND THE CYLINDER DEFINED BY SAID OUTER SIDE WITH THE RADIAL EXTENT BEING SUFFICIENT TO PROVIDE THAT WHEN SAID METAL IS HARD IT CAN BE INSPECTION-CUT ON A TURNING MACHINE WITHOUT CUTTING SAIE INSERT RING WHILE CUTTING UNIFORMLY ALONG THE ENTIRE LENGTH OF SAID PISTON, SOLIDIFYING SAID MOLTEN METAL, INSPECTION-CUTTING SAID PISTON ON A TURNING MACHINE ALONG THE LENGTH OF SAID PISTON AND TO A RADIAL DEPTH SHORT OF SAID INSERT RING, FINISH TURNCUTTING SAID PISTON AND SAID INSERT RING ALONG THE ENTIRE LENGTH OF SAID PISTON AND TO A RADIAL DEPTH SUFFICIENT TO FINISH-CUT SAID OUTER SIDE OF SAID INSERT RING, AND CUTTING A GROOVE IN SAID INSERT RING FOR RECEPTION OF A PISTON RING. 